1. Field of the Invention
The invention relates to a three-dimensional computer graphics technology, and more particularly to a method of creating a texture.
2. Description of the Related Art
In the field of computer graphics (CG) or three-dimensional graphics in particular, a texture mapping technology is used to achieve graphics having higher resemblance to actual live images. In the texture mapping technology, images called textures, which imitate actual matters, are pasted onto the surfaces of objects rendered in simple polygons.
For example, when a game program with three-dimensional graphics display presents cave rocks or human skin, textures containing image data for imitating the physical texture of a rock or skin are mapped onto the surfaces of polygons to generate photorealistic images. Moreover, to express pits and projections on the surfaces of objects, a technique called bump mapping is also used. In this technique, matters are shown as if having uneven surfaces although the three-dimensional models have flat surfaces.
When a certain pattern or asperities need to be repeated on a wide range of the surface of a matter, a unit texture is mapped repeatedly. Here, the boundaries of the unit texture may appear inappropriately noticeable unless the unit texture is created so as to show a continuous pattern across adjoining unit textures.
If a game uses textures that are to be mapped repeatedly to show continuous patterns, the textures may be created in advance at the programming stage. Nevertheless, the textures created previously have a prescribed viewpoint and prescribed positions of light sources alone, and thus are sometimes inappropriate to express desired physical textures. Besides, prepared textures have only a limited capability to express the surfaces of matters when the matters vary in color or roughness with time.